It is known that chymase belongs to chymotrypsin type proteases in serine proteases and is a cytotoxic protein accumulated in secretory granules in mast cells and released upon stimulation. Further, it is recently reported in Circ. Res., 66, 883 (1994) that chymase possesses the action of converting angiotensin I into angiotensin II involved in blood pressure regulation in vivo. Further, it is also known that a chymase inhibitor inhibits release of histamine from mast cells (J. Cell. Biochem., 38, 291 (1988)) and release of a cytotoxic protein from eosinophils (Arch. Biochem. Biophys., 312, 67, (1994)). That is, it is known generally at present that chymase is involved not only in cytotoxicity but also in release of various mediators in vivo.
Further, the action of chymase varies depending on the type of animal, and it is reported that there is a great difference in the action particularly between human or dog and rodent (Proc. Natl. Acad. Sci. USA, 84, 364 (1987)).
As a compound inhibiting chymase, only an inhibitor for chymotrypsin as a digestive enzyme is known at present and is not satisfactory in inhibitory activity, selectivity of inhibition toward other proteases, stability of the compound in vivo, toxicity etc. and it has not been developed as a pharmaceutical composition. Accordingly, there is demand for a highly safe chymase inhibitor which at low concentration, selectively inhibits chymase.